Heretofore, there have been known various techniques for suppressing vibrations/noises in an automobile door. For example, the following Patent Publication 1 (Japanese Patent Laid-Open Publication No. 2003-118364) discloses a technique relating to a sound absorbing material, which is to be used for blocking the propagation of vibration from the inside of an automobile to the outside.
As a technique for preventing the occurrence of abnormal noises during closing of an automobile door or door closing, the following Patent Publication 2 (Japanese Patent Laid-Open Publication No. 10-138759) discloses an automobile door structure comprising a stopper portion provided on a door inner panel at a given position where the stopper portion is to be brought into contact with a door switch mounted on an automobile body, during door closing, so as to suppress vibrations of the inner panel during door closing.
There has also been known a technique for suppressing high-frequency sounds by use of a sound absorbing material, such as urethane, disposed inside an automobile door.